1. Field of the Invention
The present invention relates to a method of producing an ocular lens such as a contact lens or an intraocular lens, and lens blank holders and a lens blank loader/unloader, which are used in producing the ocular lens. More specifically, the present invention is concerned with such a method of producing an ocular lens by effecting cutting operations on a lens blank which gives one ocular lens, so that the produced ocular lens has desired front and back curved surfaces. The invention also relates to lens blank holders for holding the lens blank, by which the lens blank is supported on a front and a back surface cutting device during the cutting operations on the lens blank for forming an intended ocular lens having the back and the front curved surfaces. The invention also relates to a lens blank loading and unloading device for loading and unloading the lens blank on and from the front or back surface cutting device.
2. Discussion of the Related Art
In a conventional method of producing an ocular lens as disclosed in JP-A-1-101319 and JP-A-7-195556, for instance, a lens blank formed of a suitable material and having a size that gives an ocular lens is bonded to a lens blank holder, which is in turn attached to a spindle of a cutting device, so that the lens blank is machined for forming the intended ocular lens having a back and a front curved surface. In this method, one of the opposite surfaces of the lens blank is first machined while the other surface is bonded to the lens blank holder. Subsequently, the lens blank is removed from the lens blank holder, and the above-indicated other surface which has been bonded to the lens blank holder is then machined while the above-indicated one surface which has been machined is bonded to the lens blank holder. Thus, the opposite surfaces of the lens blank are machined to give the desired back and front curved surfaces of the ocular lens.
In the method indicated above, however, it is required to bond the lens blank to the blank holder, remove the lens blank therefrom, and clean the lens blank to remove the bonding agent after each of the opposite surfaces of the lens blank has been subjected to the cutting operation. Accordingly, the above method is cumbersome and time-consuming, resulting in low production efficiency of the ocular lens. The cutting operations on the lens blank need to be effected by taking account of the thickness of a layer of the bonding adhesive applied between each surface of the lens blank and the blank holder. However, it is difficult to effect the cutting operations on the lens blank for forming the ocular lens with high accuracy while accurately controlling the thickness of the adhesive layer. In some cases, the thickness of the obtained ocular lens may vary due to a variation of the thickness of the layer of the adhesive applied between the lens blank surface and the lens blank holder.
When the lens blank is bonded to the blank holder, the axis of the lens blank needs to be accurately positioned relative to the axis of the spindle of the cutting device, so that the produced lens has an optical axis. However, no technique has been established for assuring accurate and easy positioning of the lens blank relative to the blank holder when the lens blank is bonded to the lens blank holder. It is accordingly difficult to accurately position the lens blank relative to the spindle of the cutting device.